1. Field of the Invention
The present invention relates to an imaging device which processes a pixel output of an imaging element utilizing parts of pixels as a focus detecting element of a phase difference system to detect a focus state, a camera system and an image processing method.
2. Description of the Related Art
A suggestion concerning an imaging device which utilizes parts of pixels of an imaging element as a focus detecting element to detect a focus state has been made in, for example, the publication of Japanese Patent No. 3592147. The imaging device of the publication of Japanese Patent No. 3592147 sets the parts of the pixels of the imaging element to focus detecting pixels, forms images of subject luminous fluxes passed through different pupil regions symmetric to an optical axis center of a photographing lens in the focus detecting pixels, and detects a phase difference between the subject luminous fluxes to detect the focus state of the photographing lens.
Regions of parts of the focus detecting pixels are shielded from light. Therefore, pixel outputs of the focus detecting pixels are pixel outputs whose light is decreased as compared with normal pixels. It is known that a quantity of the light to be decreased in the focus detecting pixels changes in accordance with optical characteristics concerning the focus detecting pixels. Thus, the publication of Japanese Patent No. 4770560 has suggested that the pixel outputs of the focus detecting pixels are corrected in accordance with the optical characteristics.